The present invention relates to a mother glass board used to produce a plurality of transparent insulator substrates.
Referring to FIG. 1, a conventional circuit configuration of an active matrix type liquid crystal display (LCD) 100 will now be described. The LCD 100 comprises a display panel 101, a gate driver 103 and a drain (data) driver 104.
The display panel 101 has a plurality of gate wirings (scanning lines) G1xe2x88x92Gn and Gn+1xe2x88x92Gm and a plurality of drain wirings (data lines) D1xe2x88x92Dn and Dn+1xe2x88x92Dm. The gate wirings G1xe2x88x92Gm and drain wirings D1xe2x88x92Dm orthogonally cross forming pixel 102 at each point of intersection. The gate driver 103 is connected to the gate wirings G1xe2x88x92Gm to supply a gate signal (a scanning signal) thereto. The drain (data) driver 104 is connected to the drain wirings D1xe2x88x92Dm to supply a data signal (a video signal) thereto.
The drivers 103 and 104 form a peripheral drive circuit 105. A liquid crystal display, which includes the display panel 101 and at least one of the drivers 103 and 104 formed on an insulator substrate, is generally called a driver built-in liquid crystal display. The gate driver 103 or drain driver 104 may be provided on both sides of the display panel 101.
FIG. 2 shows an equivalent circuit for the pixels 102. Each pixel 102 comprises a TFT (Thin Film Transistor) 106, a liquid crystal cell LC and a supplemental capacitor (a storage or added capacitor) SC. The TFT 106 comprises a gate connected to the gate wiring Gn, a drain connected to the drain wiring Dn and a source connected to the supplemental capacitor SC and a display electrode (pixel electrode) 107 of the liquid crystal cell LC. The liquid crystal cell LC and supplemental capacitor SC form a signal storage element.
The liquid crystal cell LC has the display electrode 107 and an opposite electrode 17. The opposite electrode 17 is applied to a voltage of Vcom. The opposite electrode 17 is common to all of the pixels 102 and is also called a common electrode. The display electrode 107 and the opposite electrode 17 produce capacitance therebetween. The supplemental capacitor SC comprises a storage electrode 109 connected to the source of TFT 106 and a supplemental capacitor electrode 110. A constant voltage VR is applied to the supplemental capacitor electrode 110. The supplemental capacitor electrode 110 may be connected to the gate wiring Gn+1 adjacent to Gn.
Referring to FIG. 3, a partial cross-sectional view of the LCD 100 will now be described. The LCD 100 comprises opposing transparent insulator substrates 11 and 12, which are preferably made of glass material. A liquid crystal layer 13 filled with liquid crystal is provided between the substrates 11, 12. An aluminum alloy film 14 forming a wiring layer, an inter-layer insulating film 15 and an orientation film 16 which is preferably made of polyimide resin are laminated in the substrate 11. On the substrate 12, the opposite electrode 17 preferably made of an ITO (Indium Tin Oxide) film is formed, and a second orientation film 18 preferably made of polyimide resin is laminated.
Between the orientation films 16 and 18 on the peripheral portion of the insulated substrates 11 and 12, a sealing material 19 preferably made of epoxy resin is provided to prevent leakage of the liquid crystal of the liquid crystal layer 13.
A part of the aluminum alloy film 14 extends to the edge of the substrate 11 and forms a contact pad 20. The contact pad 20 may be a laminate of ITO and chromium (Cr) and be different from the film 14. A part of the opposite electrode 17 extends to the edge of the substrate 12 and forms a contact portion 22. The contact portion 22 is connected to the contact pad 20 with a conductive material 21. The voltage Vcom is applied to the contact pad 20. The voltage Vcom is supplied from the film 14 to the opposite electrode 17 via the conductive material 21 and the contact portion 22. The conductive material 21 is preferably made of resin mixed with conductive material.
As described above, the opposite electrode 17 formed on the peripheral portion of the substrate 12 is connected to the contact pad 20 formed on the border of the insulator substrate 11 via the conductive material 21. This arrangement facilitates wirings when mounting the liquid crystal display in various apparatus, such as a personal computer, a word processor, or an electronic notebook, using the contact pad 20 as a pad for the voltage Vcom, a power supply pad VR, a power supply pad for the peripheral drive circuit 105, and an input pad for a data signal. A plurality of the insulator substrates 11 and 12 are produced from one large plate glass (a mother glass board).
As shown in FIG. 4(a), a plurality of the insulator substrates 12 (12a-12d) are formed in square formation regions arranged in a matrix form on a mother glass board 31. The contact portions 22 of the opposite electrodes 17 of the adjacent substrates 12a-12d are connected to one another on the mother glass board 31. The board 31 is cut along the dotted line in FIG. 4(a) to provide separate insulator substrates 12, as shown in FIG. 4(b). When the substrates 12a-12d are cut from the mother glass board 31, the continued contact portions 22 of the opposite electrodes 17 are also cut off. Consequently, the edges of the contact portions 22 of the opposite electrodes 17 are exposed of extend outward from the border of the insulator substrate 12.
When the insulator substrates 12a-12d are cut away from the mother board, adhesion of the contact portions 22 to the substrates 12 is decreased by the stress applied to the mother board 31, especially by the external force concentrated at the periphery of the substrates 12a-12d. This permits moisture or contaminants to intrude into a clearance between the contact portions 22 and the substrates 12, decreasing the display performance and reliability. Moreover, such contaminants may corrode the opposite electrodes 17 and affect the liquid crystal layer 13 and the TFT 106.
Accordingly, it is an object of the present invention to provide a mother glass board for fabricating a liquid crystal display with improved reliability.
To achieve the above objective, the present invention provides a glass board for forming a plurality of liquid crystal display panels, comprising: a plurality of insulating substrates; an electrode formed on each of the insulating substrates, each of the electrodes having a main body portion, a peripheral edge and at least one contact portion extending from the peripheral edge, wherein the contact portions of adjacent insulating substrates are spaced from each other by a predetermined distance.
The present invention further provides a glass board for forming a plurality of liquid crystal display panels, comprising: a plurality of insulating substrates; an electrode formed on each of the insulating substrates, each of the electrodes having a main body portion, a peripheral edge and at least one contact portion extending from the peripheral edge, wherein the contact portions of adjacent insulating substrates are spaced from each so that when the insulating substrates are separated from each other, adhesion of the contact portions to their respective substrate is not compromised.
The present invention further provides a liquid crystal display apparatus comprising: a substrate; and a common electrode for liquid crystal cells located on the substrate within each formation region; wherein an end of each common electrode is located within the associated formation region such that adjacent ends of adjacent substrates are spaced from each other.
Other aspects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings illustrating by way of example the principles of the invention.